Journal of Equine Veterinary
Science, Vol. 7, #2: 1987
Reprinted with permission, ©1987
Veterinary interest in dimethyl-sulfoxide (DMSO) and
its derivative methylsulfonylmethane (MSM) has increased
in recent years. Topical use of DMSO is FDA approved,
but as internal use of DMSO increases (such as IV injections)
researchers and practitioners are turning to MSM because
of the absence of the objectionable taste/smell. Sometimes
referred to as DMSO2, MSM is a stable, odorless
and colorless crystalline end product of the methyl-S-methane
chemical series.5 This series of compounds
has been recently determined to be an important supplier
of bio-available sulfur to the earth's plant and animal
MSM can be administered orally to horses and other animals
without rejection due to unusual smell or taste. Although
the use of MSM has been mostly for prophylaxis of just
about every unhealthy condition,4 those who
have prescribed MSM make many claims as to the benefits
it brings to the patient. While, these claims tend to
make me skeptical, nevertheless, we have published several
articles over the years about this seemingly amazing product.
Some of the potential pharmacological uses of MSM are:
- Moderating allergic reactions.
- Moderating gastrointestinal tract upset from many
causes, including diet and oral drugs.
- Correcting malabsorption of other nutrients such as
minerals whose imbalance relate to problems such
- Antiparasitic action.
- Pain and inflammation relief.
- Natural antimicrobial and antioxidant.
Without FDA approval, it is natural to worry about toxicology.
The published data, together with methyl-sulfonylmethane's
historical presence in plants and animals is encouraging.
Dr. John Metcalf, who has used the product for years,
says "we are dealing with quite a safe substance."4
Using radiolabeled S35, quite a bit has been
learned about MSM movement and metabolism in the body.
Taken orally, a portion binds to receptor sites of the
mucosal membranes. Any excess is absorbed, passing to
the blood and then to the unit body structures, or cells.
It quickly crosses the cell membrane and can thereafter
be found in the inner or subcellular fractions including
nuclear, mitochondrial, lysosomal and microsomal structures.
In specialized structures within these cells, the sulfur
is biotransformed into the multitude of organo-sulfur
molecules required by the horse in good health. In mammals,
MSM not metabolized is eventually excreted by the renal
pathway, and through perspiration and respiration. Only
traces pass with the feces.2
While sulfur is required by both plants and animals,
neither can use elemental sulfur directly. Dr. Robert
Herschler, a leading MSM researcher, believes that methyl-S-methanes
are important sources and storage forms of bioavailable
sulfur for both plants and animals. Following ingestion
of S35 labeled MSM, every normal organo-sulfur
compound so far isolated assays positive for the incorporated
label. This confirms both bio-availability and nonselective
utility. MSM donates sulfur for the biosynthesis of both
methionine and cysteine, important protein-building blocks.
Sulfur derived from MSM is also found in keratin, (hoof,
horn and hair protein), serum albumins, connective tissue,
immunoglobulin G and transferrin. Sulfur bonds, derivable
from MSM, also sustain proper conformation of specific
enzyme molecules; an absolute requirement for proper function.
This means MSM is the most stable and convenient source
of the macronutrient supplement for the horse. It is a
readily accepted food, and is legally marketed as such.3
It has been suggested that most mammals are chronically
deficient in bio-available sulfur, as young horses fed
a ration of MSM seem friskier, huskier and simply look
Classified as a drug, MSM falls under the jurisdiction
of the FDA. But, as a food, it does not. There are substances,
such as sodium chloride, which can be considered both
a food and a drug. Sprinkled on your eggs in the morning,
salt is a food. Dissolved in sterile water and given IV,
salt is a drug. Currently the daily amount of MSM given
as a food (on grain) is two heaping teaspoonfuls night
and morning. It works best if the powder is dissolved
first in warm water and then poured over the grain. Used
orally as a drug, the dosage of MSM may be as high as
100 grams, or more, per week.
DMSO and MSM have tremendous potential in improving equine
health. The third decade of research on these products
is beginning, yet political barriers still block their
widespread use as legal drugs. The non-medical biological
uses for these products steadily unfold, demonstrating
an amazing diversity of applications.1
1. Jacob SW and Herschler R: Introductory
remarks: DMSO after twenty years. An NY Acad Sci
2. Herschler, RJ Personal communication.
3. Herschler, RJ MSM - A nutrient for the horse. Eq
Vet Data 7(7) 268, 1986.
4. Metcalf, JW. MSM - Status report. Eq Vet Data
7(21) 332-333, 1986.
5. Metcalf, JW. MSM - A dietary derivative of DMSO. J
Eq Vet Sci 3(5), 148.1983.